Trap circuit control for railway signals



Sept. 7, 1948. E. M. ALLEN TRAP CIRCUIT CONTROL FOR RAILWAY SIGNALSFiled April 5, 1947 WA, m T P. A MN mm Nm QN QN M w QW* 3f m] w @mi 5jQT. QN. No, w m m N E u m mum@ REN, 93 n e awww ma 5N. r, wij@ Q m@ NSWN\\ N Nm, N .b

Patented Sept. 7, `1 948 TRAP CIRCUIT CONTROL FOR RAILWAY SIGNALS EarlM. Allen, Pittsburgh, Pa., assigner to The Union Switch & SignalCompany, Swissvale, Pa., a corporation of Pennsylvania Application April5, 1947, Serial No. 739,569

6 Claims.

My invention relates to trap circuit control for railway signals, andparticularly to an arrangement of circuits for providing continuouscontrol of railway signals by a train on a stretch of track whichincludes a dead section in an otherwise continuous series of trackcircuited sections.

In some situations such, for example, as where one railway crossesanother railway which has a plurality of tracks, the rst railway has asection through the multiple track crossing which cannot be providedwith a track circuit and which is longer than the shortest train whichmay be run on the first railway. It is therefore possible for a shorttrain to occupy this section, known as a dead section, at the crossing,without shunting any track circuit. In such a situation, it is commonpractice to use an arrangement of circuits to provide what is known astrap circuit control, through which a signal for the first railway iscontrolled by a train on the rst railway approaching the crossing toindicate stop when the train passes the signal, and to continuouslyindicate stop while the train is wholly on the dead section and untilthe train has passed through the first section beyond the dead section.

One feature of my invention is the provision of a directional trapcircuit arrangement, in which a trap circuit stick relay, which becomesdeenergized when a train moves from an approach section wholly onto adead section, can again become energized only in response to the trainpassing from the dead section into an adjacent approach section andcannot become energized by a second train entering the opposite end ofvan adjacent approach section.

Another feature of my invention is the provision of circuits forcontrolling a trap circuit stick relay arranged so that the trap circuitstick relay will become deenergized by only a train that is short enoughto be wholly on lthe dead section. A train that is long lenough that,all the While it is passing over the dead section, it extends over ontoone of the adjacent sections, will not deenergize the trap circuit stickrelay.

I shall describe one form of apparatus em-` bodying my invention, andshall then point out the novel features thereof in claims.

TheL accompanying drawing is a diagrammatic View showing one form ofapparatus embodying my invention, in which each of the two Vtracksections adjoining the ends of a dead section is provided with a trackcircuit including a track relay connected across its end which adjoinsthe dead section, and also including a second track relay connectedaround an insulatedfjoint in one of its rails; and in which directionalcontrol oi a trap circuit stick relay is effected by these track relaysand by a slow pick-up and slow release relay for each track circuitcontrolled by its track relays.

Similar reference characters refer to similar parts in the drawing.

Referring to the drawing, a single track railway is shown crossing amultiple track railway designated by the reference character L. Rails iand la ci the single track railway are divided by insulated joints 2 toform a section a-b adjoining one end of a dead section b-c, and a secondsection c-d adjoining the opposite end of dead section b-c. The rail ofone side of each of the sections a-b and c--d is also ldi vided by anYinsulated joint 3 to form subsections 5T and AST of section (L -b, andsubsections ET and AST of section c-d.

Section a-b is provided with a track circuit including a track relay A5Rconnected across the end of section a-`b which is adjacent one end ofthe dead section o o, and including a suitable source of current such asa battery 4- connected across the opposite end of the section, and alsoincluding a second track relay 5R connected around its insulated joint3. Section c-d is provided with a similar track circuit including atrack relay ABR connected across the end of section c-d Vwhich isadjacent the opposite end of the dead section bc, and including abattery 4 connected across the opposite end of the section, and alsoincluding a second track relay 6R connected around its insulated joint3. Asignal, designated by the reference charac--v ter 5S,'is locatedadjacent the battery end of sectiona-b for governing traflic movementstowards the right, as shown in the drawing, which I shall assume is theeastbound direction. A second signal SS is located' adjacent the batteryend of section c-'d for governing traiiic movements in the opposite orwestbound direction. Signals 5S and GS may be of any suitable designsuch, for example, as the Well-known searchlight type. l

A slow pick-up and slow release relay, designated by the referencecharacter 5P, is controlled by relays A5R and 5R. A second slow pick-upand slow release relay 6P is similarly controlled by relays ASR and 6R.1

A trap circuit stick relay, designated by the reference character TPS,is controlled by the track relays and by the slow pick-up and slowrelease relays. An impedance is connected ln multiple with the windingof relay TPS in order to make this relay slow in releasing.

Having described, in general, the arrangement of the various parts ciapparatus embodying my invention, I shall now describe the circuits andoperation in detail.

As shown in the drawing, all parts of the apparatus are in the normalcondition, that is, the track sections are unoccupied, and thereforetrack relays SR, ASR, ASR and 6R aire energized; relays SP, SP and TPSare also energized; and signals SS and SS are displaying a proceedindication.

The circuit by which relay 5P is energized passes from terminal B of asuitable source of current, through the front point of contact I ofrelay ASR, and the winding of relay SP to terminal N of the same sourceof current. Relay 6P is energized by a similar circuit passing fromterminal B, through the front point of contact I of relay ASR, and thewinding of relay 6P to terminal N.

Relay TPS is energized by a stick circuit passing from terminal B,through the front point of contact 9 of relay ASR, contact I of relay6P, front point of contact II of relay ASR, contact I2 of relay SP,Contact I3 of relay TPS, and the winding of relay TPS in multiple withimpedance 1 to terminal N.

The circuit by which signal SS is controlled to display a proceedindication includes contacts I4, IS, I6, I'I and I8 of relays SR, ASR,ASR, SR and TPS, respectively, and the mechanism of signal SS toterminal N. The circuit by Which signal SS is controlled to display aproceed indication includes contacts I9, 20, 2l, 22 and 23 of relaysTPS, SR, ASR, ABR and 6R, respectively, and the mechanism of signal GSto terminal N.

I shall assume that an eastbound train which is shorter than deadsection b-c approaches signal SS. This train, upon entering sectiona--b, deenergizes relays SR and ASR. Relay ASR, upon becomingdeenergized, opens, at the front point of its contact 'I, the circuitpreviously traced for energizing relay SP. A second circuit is nowcompleted for energizing relay SP, however, passing from terminal B,through the back point of contact 'I of relay ASR, back point of contact8 of relay SR, and the winding of relay SP to terminal N. Relay SP, onaccount of being slow releasing, does not permit its contact I2 to openduring the interval between the opening of the iirst circuit and theclosing of the second circuit for energizing this relay.

Relay ASR, upon becoming deenergized, opens, at the front point of itscontact I I, the stick circuit previously traced for relay TPS, and thencloses, at the back point of its contact II, a second stick circuit forrelay TPS passing from terminal B, through the front point of contact 9of relay ASR, contact I0 of relay SP, back point of `contact II of relayASR, contact I3 of relay TPS, and the winding of relay TPS in multiplewith impedance r to terminal N. Relay TPS, on account of being slowreleasing, does not permit its front contacts to open during theinterval between the opening of the front point of contact II of relayASR and the closing of the back point of this contact.

With relays ASR and SR deenergized, the circuit for signal SS is nowopen at contacts I6 and I1, respectively, causing signal SS to displaythe stop indication. Likewise, contacts 20 and 2IA of relays VSR andASR, respectively, are open in the 4 circuit for controlling signal BS,and therefore the arm of signal SS will now also display the stopindication.

When the rear end of the train passes insulated joint 3 of section a-b,relay SR becomes energized, thereby completing a pick-up circuit forrelay TPS, this circuit passing from terminal B, through the back pointof contact 'I of relay ASR, iront point of contact 8 of relay SR, andthe winding of relay TPS in `multiple with impedance r to terminal N.Relay SR, upon becoming energized, opens, at the back point of itscontact 8, the second circuit traced for energizing relay 5P, and,therefore, relay SP becomes deenergized.

When the rear end of the train leaves section a-b, relay ASR againbecomes energized, thereby opening, at the back point of its contact 'I,the pick-up circuit previously traced for relay TPS and opening, at theback point of its contact I I, the second stick circuit traced for relayTPS. Relay SP is now again energized by the circuit iirst traced forthis relay through the front point of contact 'I of relay ASR. Onaccount of relay SP being slow to pick up, the front contacts of relayTPS will open between the time of the opening of contact I I of relayASR at its back point and the closing of contact I2 of relay SP. Withrelay TPS noW deenergized, the circuits for signals SS and SS remainopen at contacts I8 and I9, respectively, of this relay while the trainis entirely on dead section b-c.

When the front end of the train enters subsection AST, relay ASR becomesdeenergized, thereby opening, at the front point of its contact 1, thecircuit previously traced for relay SP, causing relay 6P to becomedeenergized, With relay AGR deenergized, a second pick-up circuit is nowcompleted for relay TPS, this circuit passing from terminal B, throughthe back point of contact 'I of relay ASR, front point `of contact 8 ofrelay 6R, and the winding of relay TPS and impedance r to terminal N. Athird stick circuit is now completed for relay TPS, this circuit passingfrom terminal B, through the back point of contact 9 of relay ASR,contact I3 of relay TPS, and the winding of relay TPS and impedance 1 toterminal N. With relay ASR deenergized, the circuits for signals SS andSS are now open at contacts IS and 22, respectively, of relay ASR.

When the front end of the train enters subsection ST, relay 6R becomesdeenergized, thereby opening the second pick-up circuitr previouslytraced for relay TPS, which however now remains energized by its thirdstick circuit previously traced. A second circuit isV now completed forenergizing relay 6P, this circuit passing from terminal B, through theback point of contact 'I of relay ASR, the back point of contact 8 ofrelay SR, and the winding of relay EP to terminal N. With relay BRdeenergized, the circuits for signals SS and 6S are now open at contactsI4 and 23, respectively, of relay 6R as well as at contacts IS and 22 ofrelay ASR.

When the train leaves section c-d, relays ASR and 6R again becomeenergized. The second circuit traced for energizing relay SP is therebyopened, and the first circuit traced for this relay is then againclosed. The third stick circuit traced for relay TPS is opened at theback point of contact 9 of relay ASR, and the rst stick circuit tracedfor this relay is again closed through the iront point of contact 9 ofrelay AGR. With all track relays and relay TPS now energized, theportions of the circuits shown for controlling sigcausing relay 5P tobecome deenergi'zed. The' first pick-up circuit traced for relay TPS isnow completed through the back point of contact 1 of relay ASR, andhence relay TPS becomes energized. The second stick circuit traced forrelay TPS through the back point of contact I l of relay ASR is thenalso again closed.

When the rear end of the train enters subsection 5T, relay 5R becomesdeenergized, thereby opening the first pick-up circuit traced for relayTPS which, however, remains energized by its second stick circuit. Relay5P is now energized by its second circuit through the back points ofcontacts 1 and!! of relays AER and 5R, respectively.

When the train leaves section a-b, relays A5R and 5R again becomeenergized, and relay 5P is now again energized by the circuit firsttraced for this relay through the front point of contact 'I of relayABR.. The second stick circuit traced for relay TPS is now opened andthe first stick circuit traced for this relay is again closed. With alltrack relays and relay TPS now energized, the portions of the circuitsshown for signals 5S and GS are again closed and, therefore, all partsof the apparatus are again in the normal condition.

I shall again assume that a short eastbound train moves through sectiona-b, and that it stops wholly on section b-c, causing relay TPS to bede'energized, as previously described. I shall assume further that afollowing eastbound train, although attempting to stop in response tothe stop indication displayed by signal 5S, actually does not succeed ingetting stopped until its front en-d has entered subsection 5T. Thefirst circuit traced for relay 5P will now be opened and its secondcircuit will be closed, Both the pick-up circuits previously traced forrelay TPS remain open, and therefore relay TPS does not now becomeenergized.

It follows that relay TPS, after being deenerglzed when a short trainmoves wholly onto section b--c, can again become energized only inresponse to a train moving from section b-c into section a-b or c-d, andnot by a second train entering either section a-b or c-d from theopposite end.

I shall now assume that an eastbound train which is longer than deadsection b--c moves through section a-b into section b-c. Since the trainis longer than section b-c, its front end will enter section c-d beforethe rear end leaves section a-b. The second pick-up circuit for relayTPS is therefore closed while its front contacts are still closed by itssecond stick circuit or its first pick-up circuit, and hence relay TPSdoes not become deenergized. When the train leaves section a-b andcontinues through section c-d, the various parts of the apparatusoperate as previously described when a short train moves through sectionc--d.

If, instead of proceeding through section c-d, the long train, after itsfront end has entered subsection AST, stops, and then backs pastsignal5S, relay TPS will continue energized'. After the train leavessection c-d, all parts of the apparatus will operate as previouslydescribed when a short train backs through section a-b.

Although I have herein shown and described only one form of apparatusembodying my invention, it is understood that various changes andmodications may be made therein within the scope of the appended claimswithout departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a control arrangement for a trap stick relay in a railway signalcontrol system for a stretch of railway track divided into a rst and asecond section and also a dead section between said first and secondsections, the combination comprising, an insulated joint in one side ofeach of said flrst and second sections, a track circuit for each of saidrst and second sections each including a track relay connected acrossthe rails of the end of its section which is adjacent said dead sectionand including a source of current connected across the rails of theopposite end of its section and also including a second track relayconnected around the said insulated joint in one side of its section, afirst and a second pick-up circuit `for said trap stick relay one ofwhich is controlled by a back contact of the first track relay and by afront contact of the second track relay for one of said track circuitsand the other of which is similarly controlled by the track rclays fcrthe other track circuit, a slow pick-up and slow release relay for eachof said track cirn cuits each having an energizing circuit controlled bya front contact of the first track relay for its section and each alsohaving a second energizing circuit controlled by back contacts of both'track relays for its section, a stick circuit for said trap stick relaycontrolled by front contacts of both said slow pick-up and slow releaserelays and by front contacts of both of said rst track relays,V

a second stick circuit for said trap stick relay controlled by a backcontact of the first track relay for one of said sections, and a thirdstick circuit for said trap stick relay controlled by a back contact ofthe first track relay for the other section.

2. In a control arrangementl for a trap stick relay in a railway signalcontrol system for a stretch of railway track divided into a first and asecond section and also a dead section between sai-d rst and secondsections, the combination comprising, an insulated joint in one side ofeach of said iirst and second sections, a track circuit for each of saidfirst and second sections each including a track relay connected acrossthe rails of the end of its section which is adjacent said dead sectionand including a source of current connected across the rails of theopposite end of its section and also including a second track relayconnected around the said insulated joint in one side of its section, aslow pick-up and slows7 release relay for each of said track circuits,means for each track circuit controlled by a front contact of its iirsttrack relay or by back contacts of both its track relays for energizingits slow pick-up and slow release relay, means controlled by a trainapproaching said dead section through either said rst or said secondsection for retaining said trap stick relay energized, means controlledby the slofw pick-up and slow release relay for each track circuit fordeenergizing said trap stick relay when a train passes from its sectioninto said dead section. and means controlled by the iirst track relay'for each of' said track circuits for again energizing said trap stickrelay when a train enters its section from said dead section.

3. In a control rarrangement for a trap stick relay in a railway signalcontrol system for a stretch of railway track divided into a first and asecon-d section and also a dead section between said rst and secondsections, the combination comprising, an insulated joint in one side ofeach of said rst and second sections, a track circuit for each of saidfirst and second sections each including a track relay connected acrossthe rails of the end of its section which is adjacent said dead sectionand including a source of current connected across the rails of theopposite end of its'section and also including a second track relayconnected around the said insulated joint in one side of its sec-tion,means controlled by the first track relay for each track circuit inresponse to a train in its section approaching said dead section forretaining said trap stick relay energized, means controlled by bothtrack relays for each track circuit in response to a train moving fromits section into said dead section for deenergizing said trap stickrelay, and means controlled by both track relays for each track circuitin response to a train moving into its section from said dead sectionfor `again energizing said trap stick relay.

4. In a control arrangement for a trap stick relay in a railway signalcontrol system for a stretch of railway track divided into a rst and asecond section and also a dead section between said first and secondsections, the combination comprising, an insulated joint in one side ofeach of said rst and second sections, a track circuit for each of saidfirst and second sections each includin-g a track relay connected acrossthe rails of the end of its section which is adjacent said dead sectionand including a source of current connectedv across the rails of theopposite end of its section and also including a second track relayconnected around the said insulated joint in one side of its section,and means controlled by said track relays for retaining said trap stickrelay energized while a train is approaching said dead section and fordeenergizing said trap4 stick relay when a train moves from either ofsaid first and second sections into said dead section and also for againenergizing said trap stick relay when a train moves from said deadsection into either said first or said second section.

5. In a control arrangement for a trap stick relay in a railway signalcontrol system for a stretch of railway track divided into a first and asecond section and also a dead section between said rst and secondsections, the combination comprising a track circuit for each of saidfirst and second sections, means controlled by said track circuits inresponse to a train approaching said dead section for retaining saidstick relay energized, means controlled by said track circuits inresponse to a train moving from said first or said second section intosaid dead section for deenergizing said trap stick relay, and meanscontrolled by said track circuits in response to a train entering saidiirst or said second section from said dead section for again energizingsaid trap stick relay.

6. In a control arrangement for a trap stick relay in a railway signalcontrol system fora stretch of railway track divided into a first andasecond section and also a dead section between said rst and secondsections, the combination comprising, a slow ,pick-up and slow releaserelay for each of said first and second sections energized when theassociated section is unoccupied, means responsive to a train in each ofsaid rst and second sections approaching said dead section for retainingsaid trap stick relay energized, means responsive to a train in each ofsaid rst and second sections approaching said dead section for at rstenergizing and then deenergizlng the associated slow pick-up and slowrelease relay, means controlled by each of said slow pickup and slowrelease relays for deenergizing said trap stick relay when a train movesfrom the associated iirst or second section into said dead section, andmeans responsive to a train entering either of said iirst or secondsections from said dead section for again energizing said trap stickrelay.

EARL M. ALLEN.

